diff --git a/Include/ceval.h b/Include/ceval.h
index 3735f00..f461601 100644
--- a/Include/ceval.h
+++ b/Include/ceval.h
@@ -145,6 +145,7 @@
 #endif /* !WITH_THREAD */
 
 PyAPI_FUNC(int) _PyEval_SliceIndex(PyObject *, Py_ssize_t *);
+PyAPI_FUNC(int) _PyEval_SliceIndexNotNone(PyObject *, Py_ssize_t *);
 
 
 #ifdef __cplusplus